According to this week's AvWeek, DoD test & evaluation people listed several
concerns about the F/A-22. The test fleet is getting more and more different
from the production baseline, firecontrol problems and some hardware and
software reliability problems. No mention of flutter.

The same article said that the test community was getting increasingly
concerned about 35mm cannon firing modern (AHEAD or 4P) ammunition as a
threat to low fliers, especially helos.